1. Field of the Invention
This invention relates to acrylic cationic latices and the methods of preparing and using the same.
2. Brief Description of the Prior Art
Cationic latices are known in the art and their method of preparation involving free radical emulsion polymerization of monomers in water, in the presence of cationic surfactants, is also known. The free radical emulsion polymerization procedure generally results in high molecular weight polymeric products which are normally in the range of 100,000 to several million. In this molecular weight range, the latices possess good mechanical properties. It has, however, been found that the latices leave something to be desired as to film properties relating to protective durability, i.e., the ability of coatings to maintain their integrity against chemicals, weathering, and the like. These shortcomings are due, at least in part, to the surfactants which are used in the preparation of the latices.
Surfactants are water-soluble, consequently, they render coatings prepared therefrom water-sensitive, especially when they are used in high concentrations. Surfactant, being oligomeric, can exude to the surface of the film giving an oily surface for collection of dirt. Further, the surfactants can reside at the interphase between the substrate and the film, inhibiting adhesion of the film to the surface.
In view of the foregoing, it is desirable to employ surfactant in small but effective concentrations so as to obtain stable and substantially coagulum-free latices. Surfactants which have halo acids as gegen-ions have been found very effective in this regard.
In contrast, surfactants with gegen-ions derived from organic acid, to be effective, have to be used in relatively high concentrations. The present invention provides for an organic acid which can be used in small but effective concentrations to provide latices which are free of the afore-described negatives.